Supplementary MaterialsSupplementary information develop-146-174961-s1. their polarity, suggesting that an epithelialCmesenchymal-like transition has a role in cluster generation (Hirose et al., 2006; Serluca, 2008; Tandon et al., 2016; Wu et al., 2010). Once the PE forms, the heartbeat has an essential role in allowing PE cells to be washed away into the pericardial cavity. The heartbeat generates a pericardial fluid flow, allowing the PE cells to detach from your mesothelium. Floating PE cells adhere to the myocardial surface, and ultimately spread over the surface to form the epicardium (Peralta et al., 2013; Plavicki et al., 2014). During morphogenesis, cell migration and proliferation result in the continuous rearrangement of mechanical properties of HDAC9 tissue layers. Collective cell migration and proliferation can lead to local cell crowding and the generation of tissue tension (Eisenhoffer et al., 2012; Tada and Heisenberg, 2012). Additionally, changes in tissue growth can further influence cell signaling (Aegerter-Wilmsen et al., 2012; Hiscock and Megason, 2015). The actomyosin cytoskeleton plays a central role in controlling cell shape and developmental events (Heisenberg and Bellaiche, 2013; Levayer and Lecuit, 2012; Martin et al., 2009; Munjal and Lecuit, 2014). It is tightly associated with membrane junction complexes and can react to extracellular signals or signals from neighboring cells by altering cell properties (Lecuit and Yap, 2015; Martin et al., 2010; Munjal and Lecuit, 2014). The PE comprises mesothelial cells from your dorsal pericardium (DP). Mesothelia Palmitoylcarnitine chloride share some commonalities with epithelia and it is therefore interesting to draw parallels to learn more about their development and homeostasis. Epithelial layers are managed by cell division, intercalation and extrusion (Guillot and Lecuit, 2013), which are interconnected; for instance, cell proliferation is also a major driver of cellular intercalation and thus tissue business in growing embryos (Firmino et al., 2016). Cell extrusion in epithelia is usually often Palmitoylcarnitine chloride observed during morphogenesis, including tissue folding (Ambrosini et al., 2017; Monier et al., 2015; Saias et al., 2015), and the emergence of hematopoietic cells (Kissa and Herbomel, 2010; Lancino et al., 2018). It remains unclear how canonical developmental signaling pathways can influence these cellular behaviors and whether extrusion can also be a morphogenetic event occurring in mesothelia. Here, we used zebrafish to study the morphogenetic events leading to PE formation. We found that cells from your DP collectively move towards DP midline, where some of them round up and extrude into the pericardial cavity to form the PE cluster. These processes depend on Bmp signaling, which regulates actomyosin dynamics. Our results reveal how signaling molecules influence morphogenesis and show that PE formation relies on complex tissue rearrangements within the pericardial mesothelium. RESULTS Constriction of the dorsal pericardium prospects to apical extrusion of proepicardial cells To investigate PE formation, we analyzed the movement of mesothelial cells in the pericardium of zebrafish embryos. Most PE cells appear as clusters in the DP proximal to the VP and the atrio-ventricular canal (AVC) of the heart tube (Fig.?1A). We analyzed PE formation 52?h post-fertilization (hpf), before the PE clusters are visible. For live imaging, we used the enhancer trap lines or (hereafter termed (embryo. time lapse at different time points are shown. White arrows point to PE cells (observe Movie?1). (C) First and last frame of an time lapse of DP cells in an embryo; the midline is usually shown by a dashed white collection, blue dots show tracked cells. Full colored songs label the first time frame in purple and the last in red. Arrows indicate overall direction of tracked cells. (D) The half-rose diagram shows the movement angles of tracked cells relative to the midline. (E) 3D Palmitoylcarnitine chloride projection of the divergence field calculated for the time-lapse video above. The calculated divergence values are represented by colors; purple-blue regions represent constriction and red regions represent expansion. Black arrows point to PE cell clusters. ap, arterial.